The red filter

Bobby Ironsights

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Dec 3, 2006
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Thunder Bay, ON, Canada
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What's up with the red filter?

When I bought my first enlarger, a beseler 35 printmaker, it had a filter drawer underneath on a swivel, and a small piece of very red glass.

I never used it, never gave it any thought, there was no mention of it in the instructions.

I've now purchased a used Beseler 45 MXT, and I've got to tell you, it's great to have a motorized enlarger, really nice, plus it's got lots of other bells and whistles.

It's five feet tall, and weighs more than my GF, but hey....whaddya' want eh?

It also came with an under the lens VC filter set. Nice optical glass ones, and I'm pleased as punch.

But it too has a very RED filter. It's not labelled with a grade, so I assume it must not be a VC filter.

I'm starting to wonder, is it a "focusing filter" for graded papers? Does it allow for framing, with a paper in the easel, without exposing the paper?

I won't get into the darkroom for a bit, but I'm dying to know, because that would be uber-cool.

P.S. This enlarger ROCKS!, and the nice thing is that I can store my first enlarger, in a corner of the baseboard of my new humungo enlarger! At least until I sell it.

I hear red is used in black and white for contrast.
It just prevents exposure if the lamp is on and there is paper in the easel. That's all.

I wouldn't use it for focusing because it will alter the focus point by about a third of its thickness, and it is at the wrong end of the spectrum so if there is any chromatic aberration you are using the wrong wavelength to focus. It's helpful for framing if you are doing borderless prints, though.

I was just guessing, and I take your word for it, but It seems expensive and pointless doesn't it?

I've used plenty of enlargers that don't have one, but now and then they are useful - I used them for borderless prints and occasionally for lining up complicated dodging or burning masks. How expensive are they? They can be cheap plastic or resin.


PS Do the instructions with the enlarger mention focusing with the under-the-lens filter in place if you are going to print with it?
PS Do the instructions with the enlarger mention focusing with the under-the-lens filter in place if you are going to print with it?

No, they never mentioned the red filter at all. Not one word, that's why I was guessing.

(The instruction for the printmaker said nothing about it, there are no instructions with the Beseler 45. The 45 looks really old, but the webside claims the basic design hasn't changed in decades.)
Sorry for the vague question. I was only referring to the contrast filters - or any filter used under the lens while making the exposure.

You probably know this already, but if you are going to use glass filters under the lens while printing then you should focus with one of the printing filters in place, because they affect focus. As long as you are focusing with the same type and thickness of filter, you don't have to use the exact filter for focusing that you would for printing.

The best way is to use filtration between the lamp and the negative, of course.

Good luck,
years ago most enlargers came with that crazy red filter and it was used for viewing the paper with negative in place, why , who knows.

i have taken them off of most enlarger i have owned or take care; however, on occasion they come in handy, when post flashing a small area on the paper with a white light they do come in handy as one doesn't have to find some ruby lith to use.
I had the red filter on the enlargers I learned on, and was a bit disappointed when the one I bought for myself didn't have one... it's definitely not essential, but I did appreciate it for framing.

If Bobby doesn't mind, can I hijack the thread a bit? My question is unrelated except for being about enlargers and filters, but it didn't seem worth starting a new thread over...

I recently finally got around to setting up my enlarger and making some prints... only problem is the filters (C,M,Y filters between the lamp and the light box) are looking a bit cloudy. So far, using the diffusion box, this does not seem to have caused a problem... I haven't tried the condenser box yet... now since the light has to go through the box before reaching the lens, I don't suppose it matters if the filters are not too clear... but perhaps I'm wrong. How clean do the filters need to be?
When you say 'cloudy' is it a surface effect or is the filter cloudy right through? What material are the filters made of?

What sort of an enlarger do you have? Dichroic filters can look odd but be perfectly OK to use.

Thanks for the reply Helen. It's a Fujimoto VR70. I could be wrong but I think they were mainly meant for the professional market, and I can't find a lot of info on them beyond the original paperwork.

The filters are dichroic, so I guess that might explain it. It just looked odd to me because they're kind of different degrees of cloudy... for example the yellow filter (blue-looking plate) looks pretty clean and I can see the bulb behind it... while the cyan filter looks more cloudy and you can't really see through it. The magenta filter looks cloudy too although in the centre it's clear (it looks like someone tried to wipe it)... this suggests to me that it's on the surface rather than throughout the material, but I'm still not sure I should be cleaning it... the manual doesn't seem to think so ("Do not touch the dichroic filters with your hands", and if I want to clean the filters apparently I should use canned air; "Do Not use a brush." ... :scratch:
Dichroic (aka "interference") filters aren't dyed like other filters, the filtration is usually a coating, and the thickness of it is critical because it is the thickness that controls which wavelengths are transmitted and which are reflected.

The coating can look cloudy. It should look even, but changing in appearance with angle, if that makes sense. The manual is correct: you should never touch the surface. I suggest cleaning with a hand blower rather than canned air.

Are you going to be using them for VC B&W or colour?

I guess the coating does look even on each filter, except on the magenta filter where someone has obviously touched it or tried to wipe it. In the centre of the filter, part of the coating seems to have been wiped off. I will probably never use the enlarger for colour, but definitely plan to use it for VC B&W... is this likely to cause a problem? Thanks again.

Edit: Me describing it in words isn't much use, so here's a quick snap...

Apologies for the poor photo, I just pointed a flashlight at it so the colour is a bit off and the damage may be exagerrated a bit, but at least it gives an idea... as you can see the coating is partially wiped off, but only on that central bit... most of the surface is still coated...

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